Sickle Cell Anemia
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How is Sickle Cell Anaemia Diagnosed

This article will discuss the condition of sickle cell anaemia and how is sickle cell anaemia diagnosed. Keep reading…

Sickle Cell Anemia

Sickle cell anaemia is an autosomal disorder among human beings which is caused due to a mutation in a gene called HBB present on chromosome number 11. The HBB gene is responsible for the synthesis of haemoglobin and haemoglobin transports oxygen to the red blood cells of our body. Due to the mutation in the HBB gene, it synthesizes the haemoglobin of a different molecular structure than normal haemoglobin structure which is due to a recessive gene, and this is the main reason for sickle cell anaemia.

In people with sickle cell disease, their red blood cells become deformed to ring sickle-shaped. That’s why it is called sickle cell anaemia or sickle cell disease. The oxygen transport to their red blood cells decreases due to the change in the molecular structure of haemoglobin which transports oxygen to the red blood cells. And due to the lack of oxygen red blood cells got sickle-shaped.

The bone marrow tries to make more red cells to make up for the loss but can keep up causing anaemia. Their new shape keeps on from moving properly through the body and due to changes in their shapes they get stuck to the walls of the blood vessels. These clumps of deformed red blood cells create an accidental health issue leading to no more growth causing fatigue and extreme pain.

Sickle cell anaemia originated in Africa. This disease is found all over the world, but it is mostly found in African and Asian countries. It is also known as SCA (Sickle cell anaemia) or SCD (Sickle cell disease).

Symptoms of Sickle Cell Disease

The first sign of this disease is pain in every part of the body like hands, legs, back, and chest, swelling in joints of hands and legs, many types of infections in the body, tiredness, fatigue, headache, breathlessness, shortness of breath, cold feet and hands, pallor skin or yellowish skin, jaundice, loss of appetite, dizziness. Sickle cell disease affects the body very badly.

The basic symptoms of sickle cell disease are Anemia, Vaso-occlusion, and Constitutional symptom.

Anaemia

Anaemia is a very important symptom seen in sickle cell anaemia patients. Anaemia is referred to the lack of red blood cells. Normal red blood cells are round-shaped and have a life span of 120 days but if a red blood cell becomes sickle-shaped then it cannot survive long and is destroyed within 10 to 20 days.

After sickle-shaped cells destroy, the cells of bone marrow and the cells of the spleen started to synthesize more red blood cells, but they won’t be able to fulfil this lack of red blood cells. Red blood cells will keep dying more and more and this lack of red blood cells cannot be fulfilled, due to which anaemia symptoms will be developed in the patient’s body which is a deficiency of blood in the body.

Due to the deficiency of blood, shortness of breath will also develop due to the lack of oxygen, fatigue, and delayed growth due to the lack of energy that is due to the lack of oxygen.

Obstruction

These sickle-shaped cells become sticky which they get accumulated or get stacked into the blood vessels causing obstruction or causing blockage of blood vessels due to which the organs which are waiting for blood to come to them by that blood vessel got damaged or failed. Along with this, severe pain crises in that area will be shown.

Why do Pain and Swelling Occur?

The reason behind pain and swelling is that our red blood cells are generally circular and biconcave in shape due to which their movement in capillaries and veins is very easy. But in the condition of sickle-shaped red blood cells get broken due to which they get hooked in the blood vessels and veins of the body due to which the body feels pain and if they get hooked for a long time the circulation of blood in the body is affected very badly due to which swelling occurs and due to this there is a risk of getting a heart attack.

Causes of Sickle Cell Anemia

Sickle cell anaemia is an autosomal recessive genetic disease means it can inherit from parents to their progeny. This disease occurs due to a mutation in the haemoglobin beta gene (HBB) present on chromosome number 11 which synthesizes haemoglobin, an iron-rich protein compound in red blood cells. 

Haemoglobin is composed of 4 peptide chains. Each peptide chain is bound to a heme (iron) group and different haemoglobin has different combinations of these chains. If we talk about Hemoglobin A or Hb A, it has 2 alpha globin and 2 beta-globin peptides. So, sickle cell anaemia is caused by defective or abnormal haemoglobin mainly in the beta-globin chain that has mishappened.

Mutation

A mutation is an alteration in the nucleotide sequence or the genome of an organism. So, in the case of sickle cell anaemia, the mutation is point mutation. Especially, insertion mutation in which a single nucleotide change results in codon dead codes for a different amino acid. So, these are 3 letter codes known as codons. So, each codon carries one code for the synthesis of one amino acid like CTC and GAG, both codes for Glutamic acid but, because of mutation, the code has been changed to GUG instead of GAG which is a code for valine.

So as a result, glutamic acid is replaced by valine at the sixth position of the amino acid sequence. As a result of this mutation, sickle cell is formed instead of normal biconcave red blood cells. Sickle cells can carry oxygen but the deoxygenated stage is exceeded which allows it to aggregate with other HbS proteins and form polymers that destroy the red blood cell into sickle cell. So, the process is said to be sickling.

Repeated sickling of the red blood cells damages its cell membrane and promotes premature destruction. So, it results in anaemia because of hemolysis. So, if there is hemolysis, there will be free haemoglobin in the circulation as a result increase in unconjugated bilirubin, which eventually leads to jaundice.

Why do Genetic Mutations Happen?

If one parent is normal and another one is a carrier of sickle cell disease, the chances of inheritance of disease in their children are like among 4 children, 2 babies will be normal (no disorder), 2 babies will be a carrier of the disease (sickle cell trait).

If both of the parents are a carrier of the disease, the chances of inheritance of the disease in their children are like among 4 children, 1 baby will be normal, 2 babies will be carriers, and one baby will be affected by sickle cell anaemia.

Sickle Cell Trait

As we know, sickle cell is an autosomal recessive disease. So, a mutation in both copies of the beta-globin gene is required to get sickle cell disease. So, if a person has one copy of the mutated beta-globin gene and one normal copy of the beta-globin gene then, that condition is known as sickle cell trait or sickle cell carrier.

So, a person with sickle cell trait will not have any health or clinical problem except when there become severely hypoxic, then damage develops sickle cell. So, they have some advantages like the person who mutated the beta-globin gene is less severe to malarial infection. So, in parts of the World with high malaria burdens like Africa and parts of Southern Asia where sickle cell trait has an evolutionary effect.

Types of Sickle Cell Disease

how is sickle cell anaemia diagnosed
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4 types of sickle cell disease have been found: 

  1. Haemoglobin SS disease

  2. Haemoglobin SC disease

  3. Haemoglobin SB+ (beta) thalassemia

  4. Hemoglobin SB0 (beta-zero) thalassemia

Some types of sickle cell disease are rarer and usually do not have more severe symptoms. These types of sickle cell diseases are Hemoglobin SD, Hemoglobin SE, and Hemoglobin SO. People who have these forms of sickle cell disease inherit one sickle cell gene (“S”) and one gene from an abnormal type of haemoglobin (“D”, “E”, or “O”).

Haemoglobin is a protein that allows red blood cells to carry oxygen to all parts of the body. 

1. Haemoglobin SS Disease

In this condition, the person acquires sickle cell genes from each parent, making it two genes in total. This is the most severe form of sickle cell disease. 

2. Haemoglobin SC Disease

In this condition, the person acquires one sickle cell gene from one parent, and one gene for an abnormal haemoglobin known as “C” from the other parent. This is comparatively a milder case of sickle cell disease. 

3. Haemoglobin SB+ (beta) Thalassemia

People who have this condition acquire one gene for sickle cell (“S”) from one of their parents and one gene responsible for beta-thalassemia from the other parent.  

4. Haemoglobin sb 0 (beta) Thalassemia

People who have this form of sickle cell disease inherit one sickle cell gene (“S”) from one parent and one gene for beta thalassemia, another type of anaemia, from the other parent. This is usually a severe form of sickle cell disease.

How is Sickle Cell Anaemia Diagnosed

The best test for the diagnosis of sickle cell disease is the haemoglobin test. A haemoglobin test is needed because the body gets yellowish. After this test, CBC (Complete Blood Count) test is required in which the total number of red blood cells can be identified.

After that, a Blood Smear test is required in which the shape of red blood cells is identified by different methods. After that, haemoglobin electrophoresis is required which gives a clearer picture of red blood cells. After that, to identify the mutation, an HBB gene mutation test is required.

If a person wants to know if his unborn child will be affected with sickle cell anaemia or not, then it can be identified by the baby’s amniotic fluid.

Sickling Test

The sickling test is a screening test for sickle cell anaemia or sickle cell trait. The sickling test results in two parts if the sickling cell results positive, there will be the presence of the sickling test and if the sickling cell results negative, sickling cells will be absent.

Principle of sickling test

When whole blood is mixed with a strong reducing agent such as sodium metabisulfite, deoxygenation of red blood cells does occur. If the red blood cells contain sickle haemoglobin (HbS), they become sickle-shaped.

Treatment

People suffering from sickle cell disease should use to take painkillers to kill the pain crises in their body, anti-inflammatory drugs for swelling, antibiotics to avoid repeated infections, and folic acid to prevent severe anaemia.

Hydroxyurea is an oral medication that has recently been found to help reduce the frequency of pain crises and cell anaemia. Along with these medicines, people suffering from sickle cell anaemia also require repeated blood transfusions or medicine to delay blood transfusions. Transfusions are also used to dilute HbS with normal haemoglobin to treat chronic pain, acute chest syndrome, splenic sequestration, and other emergencies.

The best treatment for sickle cell disease is a bone marrow transplant. The chances of red blood cells being deformed decrease by bone marrow transplants. Also, there will be relief from repeated blood transfusions. And this is a curable treatment of sickle cell anaemia means a bone marrow transplant can cure sickle cell disease.

Blood tests are done to start treatment as soon as possible. It is essential to get diagnosed early to get preventive care to eliminate all complications. 

Conclusion

Well, in simple terms, a simple blood test can help you diagnose sickle cell anaemia. It will check the form of haemoglobin present in your body that underlines sickle cell anaemia. 

This condition can be diagnosed in unborn babies too by collecting a little of the fluid that surrounds the baby in the womb. This fluid is known as amniotic fluid. 

 

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I am Kanika Chaudhary, a student of Biotechnology Engineering. Writing is just my hobby.